RFR: 8288001: SOURCE_DATE_EPOCH should not be set by default

[Severin Gehwolf]

On Mon, 13 Jun 2022 07:14:15 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> At default configuration, SOURCE_DATE_EPOCH is exported as environment variable in SetupReproducibleBuild. Then, gcc is affected of SOURCE_DATE_EPOCH environment variable. This value is used only to set SOURCE_DATE_ISO_8601 (except below), so I removed "export" for SOURCE_DATE_EPOCH in SetupReproducibleBuild. And, at building ct.sym, SOURCE_DATE_EPOCH environment variable is needed. So I added setting routine if SOURCE_DATE_EPOCH is not set.
>> 
>> This fix works fine. With default configuration shows -Xinternalversion output same as Windows, and with --with-source-date configuration shows -Xinternalversion output specified timestamp. Would you please review this fix?
>
> What do you mean by "build time information"?

@magicus I think it's `-Xinternalversion` which has different output between Windows and Linux of the same build. But to me that's a feature not a bug. From the PR description:

> With default configuration shows `-Xinternalversion` output same as Windows, [...]

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PR: https://git.openjdk.org/jdk/pull/9081